/*
 * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.http.client.reactive;

import java.util.AbstractSet;
import java.util.Collection;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.stream.Collectors;

import org.eclipse.jetty.http.HttpField;
import org.eclipse.jetty.http.HttpFields;

import org.springframework.http.HttpHeaders;
import org.springframework.lang.Nullable;
import org.springframework.util.CollectionUtils;
import org.springframework.util.MultiValueMap;

/**
 * {@code MultiValueMap} implementation for wrapping Jetty HTTP headers.
 *
 * <p>There is a duplicate of this class in the server package!
 *
 * @author Rossen Stoyanchev
 * @since 5.3
 */
class JettyHeadersAdapter implements MultiValueMap<String, String> {

    private final HttpFields headers;


    JettyHeadersAdapter(HttpFields headers) {
        this.headers = headers;
    }


    @Override
    public String getFirst(String key) {
        return this.headers.get(key);
    }

    @Override
    public void add(String key, @Nullable String value) {
        this.headers.add(key, value);
    }

    @Override
    public void addAll(String key, List<? extends String> values) {
        values.forEach(value -> add(key, value));
    }

    @Override
    public void addAll(MultiValueMap<String, String> values) {
        values.forEach(this::addAll);
    }

    @Override
    public void set(String key, @Nullable String value) {
        this.headers.put(key, value);
    }

    @Override
    public void setAll(Map<String, String> values) {
        values.forEach(this::set);
    }

    @Override
    public Map<String, String> toSingleValueMap() {
        Map<String, String> singleValueMap = CollectionUtils.newLinkedHashMap(this.headers.size());
        Iterator<HttpField> iterator = this.headers.iterator();
        iterator.forEachRemaining(field -> {
            if (!singleValueMap.containsKey(field.getName())) {
                singleValueMap.put(field.getName(), field.getValue());
            }
        });
        return singleValueMap;
    }

    @Override
    public int size() {
        return this.headers.getFieldNamesCollection().size();
    }

    @Override
    public boolean isEmpty() {
        return (this.headers.size() == 0);
    }

    @Override
    public boolean containsKey(Object key) {
        return (key instanceof String && this.headers.containsKey((String) key));
    }

    @Override
    public boolean containsValue(Object value) {
        return (value instanceof String &&
                this.headers.stream().anyMatch(field -> field.contains((String) value)));
    }

    @Nullable
    @Override
    public List<String> get(Object key) {
        if (containsKey(key)) {
            return this.headers.getValuesList((String) key);
        }
        return null;
    }

    @Nullable
    @Override
    public List<String> put(String key, List<String> value) {
        List<String> oldValues = get(key);
        this.headers.put(key, value);
        return oldValues;
    }

    @Nullable
    @Override
    public List<String> remove(Object key) {
        if (key instanceof String) {
            List<String> oldValues = get(key);
            this.headers.remove((String) key);
            return oldValues;
        }
        return null;
    }

    @Override
    public void putAll(Map<? extends String, ? extends List<String>> map) {
        map.forEach(this::put);
    }

    @Override
    public void clear() {
        this.headers.clear();
    }

    @Override
    public Set<String> keySet() {
        return this.headers.getFieldNamesCollection();
    }

    @Override
    public Collection<List<String>> values() {
        return this.headers.getFieldNamesCollection().stream()
                .map(this.headers::getValuesList).collect(Collectors.toList());
    }

    @Override
    public Set<Entry<String, List<String>>> entrySet() {
        return new AbstractSet<Entry<String, List<String>>>() {
            @Override
            public Iterator<Entry<String, List<String>>> iterator() {
                return new EntryIterator();
            }

            @Override
            public int size() {
                return headers.size();
            }
        };
    }


    @Override
    public String toString() {
        return HttpHeaders.formatHeaders(this);
    }


    private class EntryIterator implements Iterator<Entry<String, List<String>>> {

        private Enumeration<String> names = headers.getFieldNames();

        @Override
        public boolean hasNext() {
            return this.names.hasMoreElements();
        }

        @Override
        public Entry<String, List<String>> next() {
            return new HeaderEntry(this.names.nextElement());
        }
    }


    private class HeaderEntry implements Entry<String, List<String>> {

        private final String key;

        HeaderEntry(String key) {
            this.key = key;
        }

        @Override
        public String getKey() {
            return this.key;
        }

        @Override
        public List<String> getValue() {
            return headers.getValuesList(this.key);
        }

        @Override
        public List<String> setValue(List<String> value) {
            List<String> previousValues = headers.getValuesList(this.key);
            headers.put(this.key, value);
            return previousValues;
        }
    }

}
